How to become an online casino agent for free involves understanding the industry and establishing a network. First, research different online casinos and their affiliate programs to find one that aligns with your goals. Next, create a professional online presence through social media and a personal website. Join online forums and communities related to online gambling to connect with potential players. Promote the casino through various channels such as social media, blogs, or YouTube. Ensure to comply with legal regulations and guidelines while building your reputation as a trustworthy agent in the online casino world.